Odd partnerships among middle Eocene (Bartonian) Nummulites: Examples from the Transylvanian (Romania) and Dorog (Hungary) Basins

• Published in: Marine micropaleontology Vol. 127; pp. 86 - 98
• Main Authors: Kövecsi, Szabolcs-Attila, Silye, Lóránd, Less, György, Filipescu, Sorin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2016
• Subjects: Eocene; Larger benthic foraminifera; Marine; Nummulites; Odd pairs; Paleoecology; Paleogeography; Hungary; Romania; Eocene; Paleogeography; Paleoecology; Odd pairs; Larger benthic foraminifera; Nummulites
• ISSN: 0377-8398; 1872-6186
• DOI: 10.1016/j.marmicro.2016.07.008

Nummulites assemblages recovered from the middle Eocene of the Transylvanian Basin (Romania) and Dorog Basin (Hungary) were studied in order to infer the paleoecological structuring of the assemblages. The studied material consists mostly of A and B-generation tests of Nummulites perforatus in both basins. However, specimens of Nummulites beaumonti, and of Nummulites striatus were sporadically recorded in the Transylvanian and Dorog Basin respectively. The co-occurrence of two different Nummulites taxa, which show a striking size difference in protoconch and adult test, suggests that the small-sized Nummulites beaumonti and Nummulites striatus were the odd partners of the large-sized Nummulites perforatus during the Bartonian (middle Eocene). The co-occurrence of these closely related species might reflect their different life strategies, growth rate and/or the use of different reproduction seasons. The association of the same large partner with two distinct small-sized partners in two different, but connected basins is due to the wider paleogeographic distribution, and more abundant occurrence of the larger partner (N. perforatus), as compared to N. beaumonti and N. striatus, the smaller-sized partners. •We show that some middle Eocene Nummulites species formed odd pairs.•The odd partnership was advantageous for the smaller-sized partner.•Differences between odd pairs reflect growth rate and reproduction strategies.•The paleogeographic distribution of the odd partners is species specific.•Dominance of larger-sized partner with extrabasinal value